1. Field of the Invention
This invention relates generally to pumps such as for example end suction centrifugal pumps that have an outer casing and an internal liner. The invention is particularly suitable for slurry pumps that have an outer casing for withstanding the pressure and pipe loadings and an internal liner that is wear resistant and which in turn is supported by the outer casing.
2. Description of Related Art
Centrifugal slurry pumps typically utilise a cast outer casing made in Cast Iron or Ductile Iron with an internal liner moulded from a wear resisting elastomer compound. The casing and the liners are traditionally manufactured in two parts or halves held together with bolts at the periphery of the casing.
When assembled the two parts form a pump housing having a front side with an inlet therein and a rear side with a pumping chamber therein in which is disposed an impeller mounted for rotation on an impeller shaft. The impeller shaft enters the pumping chamber from the rear side and an outlet is provided at the peripheral side edge. The casing and liner halves are convex on the outside and have a concave shape on the inside. The liners normally have a metal skeleton moulded inside the elastomer which helps maintain its shape but also provides attachment points for bolts or studs to fix the liner into the casing halves. The two parts join along a plane which is generally perpendicular to the axis of rotation of the pump impeller.
During assembly, the two liner halves must be squeezed together at their periphery by the casing and casing bolts to effect a pressure tight seal. The resulting joint line is a vulnerable wear area in the pump, especially as the joint line is adjacent to the impeller discharge. Any misalignment of the liner halves along this joint line will produce steps or gaps in the joint line that will lead to preferential wear. Once wear starts at a local spot, the continued disturbed flow pattern at the step or gap will lead to an accelerated wear point and in the worst case localised wear will cause the liner to be worn through, thereby exposing the pressure containing casing to wear.
It is an object of the present invention to provide a pump housing assembly and including a liner which alleviates one or more of the aforementioned disadvantages.